Refining of nonferrous metals



Patented June 16, 194

REHNING F NUNFERROUS TEES James R, Stack, New Born, Staten N. Y., assignor to Nassau smelting & Reiiningilompany, Incorporated, New York, N. Y a corporation of New .Yorh

, No Drawing. Application August 1938,

Serial No. 223,215

19 Claims. (oi. 204 -109) This invention relates to the refining of nonferrous metals and more particularly to the refining of copper-bearing materials containing tin.

Considerable quantities of scrap materials containing substantial amounts of copper and lesser amounts of tin, lead,,zinc, iron and other metals are obtained from discarded materials, such as used telephone and other electrical equipment, machine shop turnings, refinery and foundry scraps and materials from various other sources. Efiorts have been made heretofore to refine these low grade materials to obtain the constituent metals therefrom in usable forms.

' In my copending application Serial No. 197,209, filed March 21, 1938, of which this application is a continuation in part, there is describeda process of refining low grade copper-bearing materials containing relatively large amounts of such material as lead, tin, and the like and smaller amounts of other metallic impurities. The aforementioned application, Serial No. 197,209, is in turn a continuation in part of application, Serial No. 91,298, filed July 18, 1936, by the present inventor, which resulted in Patent 2,111,575, granted March 22, 1938. In one process disclosed in said copending application, anodes of uch low In the production of copper cathodes by this means; it is frequentlydesirable to-maintain a substantial portion of the tin dissolved from the anodes in solution in the bath and to recover the tin from the bath either combined-with the lead from the bath as solder or as pure tin. This may be readily done when the bath is free from nickel or when the bath is operated under conditions where the tin is not strongly oxidized,

although in normal operations some tin separates from the bath and accumulates in the anode slime almost invariably produced in operations of this nature. However, when nickel is present in the bath it appears to accelerate the precipitation of the tin into the slimes by catalytic action. A similar result is obtained if an oxidizin'g agent, such as hydrogen peroxide, is added to the bath. Thus, when no nickel or oxidizing agent is present, the bulk of the tin remains disess.

solved in the electrolyte, while with'nlckel present the tin tends to go into the anode slimes.

The amount of tin precipitated into the slimes may be controlled to some extent by regulating the amount of air which has access to the electrolyte. For example, as disclosed in the aforesaid J application Serial No. 197,209, the precipitation of the tin in the presence of nickel may be inhibited to a considerable extent by covering the bath with a layer of inert oil. Molten paramn may also be used, if desired. Hence, by controlling the composition of the bath, with regard to the presenceor absence of nickel and oxidizing agents, and by regulating the amount of air that comes into contact with the bath, the operation of the electrolytic cell can be controlled to divide the anodically dissolved tin in a predetermined ratio between tin held in solution in the electrolyte and tin precipitated in anodic slime. The use of an oil or parafll'n cover on the bath to inhibit the precipitation of tin from the electrolytic bath is subject-to a number of objections. An oil may become mixed with the electrolyte if the bath is stirred vigorously and tends to form an emulsion therewith and often forms a froth which interferes with the operation of the proc- These materials. also tend to cling to the electrodes and tanks employed and, furthermore, it is diiiicult to efiect a clean separation between an oil layer and the electrolyte when this is desirable. In addition, the provision of the pro!- tective layer represents an additional item of ex pense, which it is desirable to avoid.

Heretoiore, it has, been thought advisable to keep the amounts of iron and zinc dissolved in such baths as low as reasonably possible whether nickel was present or not. However, it has been found that, when iron and zinc, either individually or together, are present in certain quantities in the electrolytic bath, the precipitation of the tin is materially retarded. This effect is especially noticeable in baths containing nickel. While the presence of these metals in these quantities does not keep all of the tin in solution when nickel is present, the amount of tin retained in solution is-greatly increased and the ratio of dissolved tin andtln precipitated in anodic slime may be controlled to a considerable extent by amount of iron and/or zinc in the simple and'effective methods for controlling the retention of tin in electrolytic baths employed in such refining methods.

Another object of the invention is the provision of electrolytic baths suitable for use in the refining of low grade copper-bearing materials containing tin.

In accordance with one embodiment of the invention, anodes are prepared of low grade copperbearing material containing a relatively large amount of tin and which may contain a substantial quantity of lead and lesser quantities of other metals, such as .arsenic, antimony, iron, zinc, nickel, etc. Theseanodes are electrolyzed for the production of pure copper cathodes in a sulphonic acid electrolyte of the type referred to hereinabove and in which iron and/or zinc are maintained in solution in quantities requisite to control the amount oftin precipitated inthe anode slime. In the present invention the iron and zinc contents of the bath are regulated to control the tin oxidation regardless of whether this oxidation is also controlled or affected by other factors, such as the presence or absence of nickel or other oxidizing agents inthe bath or of that the concentration of copper is maintained at the desired value for proper deposition and the concentration of metals other than copper does not reach the point where impure copper cathodes are produced. This may be most readily accomplished in a continuous process by removing a portion of the bath at intervals, recovering the copper therefrom, recovering the lead and tin therefrom by chemical or electrolytic methods, purifying the electrolyte and returning it to the original bath. The bulk of the copper remaining in the portion of the electrolyte being purified may be removed by electrolysis with insoluble anodes and the rest of the copper may be removed therefrom by cementing" or direct replacement with metallic tin or lead or both. The entire quantity of copper may be removed, if desired, by cementation. If tin is present in the electrolyte and it is desired to remove it subsequently by electrolysis, enough metallic tin must be added to the bath to effect a reduction of the tin in solution from the stannic to the stannous state. The copper-free liquor may then be electrolyzed to deposit either the tin or lead, if only one of these elements is present. If both tin and lead are dissolved in the liquor, they may be removed simultaneously by electrolysis as electrolytic solder.

It is obvious that, if the production of solder is tin and lead found in the starting material is recovered in useful forms having predetermined compositions.

After the removal of lead and tin, the liquor may be evaporated to remove the greater-portion of its metallic salts and the resulting strong acid is reused to make up fresh solution. The salts which are crystallized out may be worked up by any suitable method to separate the constituent metals, as well as to recover the sulphonic acid for return to the process.

The'above described and other objects and features ofthe invention will be apparent from the following detailed description of specific embodiments thereof. In practisingone embodiment of the invention, anodes are cast of material consisting essentially ofcopper, lead and tin, but

which may also include smaller amounts of nickel, zinc, arsenic. antimony, iron, etc. These anodes are electrolyzed in a sulphonic acid electrolyte in which the iron and zinc content is carefully regulated to control the oxidation of the tin dissolved therein during the operation of the process.

Among the materials which are particularly suitable for use as electrolytes in the refining of the anode metal are the aromatic sulphonic acids and very satisfactory results may be obtained by employing an acid such as phenol sulphonic acid or benzene disulphonic acid in which copper, lead, tin, zinc, iron and nickel are all-soluble. The various chloro-sulphonic and nitro-sulphonic acids may also be applied to this use. It is furthermore found that, especially when lead is present, an absence. of any appreciable amount of sulphuric acid or of sulphates is preferable.

In carrying out one process embodying the present invention, an electrolytic bath is made up containing about 350 to 500 gramsof benzene disulphonic acid per liter. Copper is then dissolved into this solution, preferably electrolytically, until 9 to 50 grams per liter of copper are present. The free acid in the bath will then range from '290 to 410 grams per liter. The above has been found to be a satisfactory and simple method of preparing' a bath according to the present invention, but other methods which have substantially the same resulting'product may well be used, e. g. dissolving 290 to 410 grams per .liter of the acid and a sumcient quantity of previously prepared copper salt of the acid to provide 9 to 50 grams of copper per liter.

The -anodes are electrolyzed in the bath described, preferably using copper starting sheets as cathodes. Preferably, the electrolyte is circulated during the electrolysis, and, also preferably, the temperature of the bath will be maintained at from 40 to 90 C. Depending somewhat upon the composition of the-anodes actually used at any given time, as well as upon the composition of the bath, and also conditions of temperature, the current density will preferably run from 8 to 25 amperes per square foot, and the cell voltage from 0.15 to 0.35 volt.

While the composition of the anodes employed may vary considerably, satisfactory results have been obtained with anodes containing from to 95% copper, .5 to 15% tin, .5 to 15% lead, and

the remainder a mixture of small amounts of other metals. Two-specific anodes which have been used successfully have'the following approximate compositions. 'Anode A86% copper, 5% tin, 7% lead, 1% zinc, and the remainder miscellaneous impurities. Anode 13-97% copper, 2% tin, and 1% iron, a

If anodes having these compositions and cone,eee ,241

taining no nickel are electrolyzed in a sulphonic acid electrolyte containing no nickel, the bulk of the anodically dissolved tin is retained in solution, and ifthe anodes or the electrolyte con-- tain nickel, the bulk of the tin would normally be precipitated in the anode slime. However, if the iron and/or zinc content of the electrolyte is made sumciently high, either by allowing these elements to build up in the bath or by adding appropriate salts thereof to the bath, the precipi tation of the tin in the anode slimes will be greatly reduced and the amount of tin retained in solution in the bath will'have a value inter may be used, if desired, but a mixture or these elements would be most readily employed and maintained in commercial operations.

It is recognized that in the normal operation of a process of this nature, even where there is zinc in the electrolyte appears to inhibitthe premediate those prevailing when nickel is absent and when nickel is present in the bath.

This is clearly illustrated by the following ta ble giving the results obtained by using various concentrations of iron and zinc in an electrolyte containing nickel:

Ni g. p. l.

Anode Per cent in solution It will be evident from this table that when substantial quantities of iron or zinc or both are present in an electrolyte containing nickel, the quantity of tin precipitated in the slimes is greatly reduced and that by varying the quantities of these elements contained in the electrolyte the tin-precipitated may be controlled over a fairly wide range, Thus, for example, when a total of approximately 3 grams per liter of zinc plus iron is present in theelectrolyte and nickel is present, about 80% of the tin precipitates in the slime, whereas, when the total of iron plus zinc in the bath is over grams per liter, the precipitated tin constitutes, 50% or less of the tin, depending upon the conditions under which the bath is operated and the amount of these elements present. In the one example in which anode B was employed and 17 grams of iron per liter and 2 grams of zinc per liter were dissolved in the electrolyte, 'only 34% of the tin precipitated out.

Thus, the amount of iron and zinc employed will depend upon the amount .of tin which it is desired to retain in solution in the electrolyte under the conditions at which the bath is operat, ing and the iron or zinc content may be from zero to such quantity as would interfere with the proper operation of the electrolytic cell. Obviously, the iron and/ or zinc dissolved in the bath may be introduced in the correct amounts as salts of these metals, or, if present in theanodes, may be allowed to build up in the bath to the desired value. Since iron and zinc are almost invariably present in impure anodes of the type used in this process, their presence must be taken into account in preparing and regulating the bath. The proper amount of iron and zinc may be maintained by adding salts thereof at intervals if the anodes do not contain them, or by removing, purifying and returning portions of the bath at intervals when iron and zinc tend to build up in the bath. Either iron or zinc alone cipitation of tin from electrolytes which contain no nickel, although the effect is' not so marked as is the case when nickel is present. As a result, by adding a suflicient quantity of iron and/or zinc to anickel-f ree electrolyte, the amount of tin precipitated inthe slimes may be reduced to a value materially below 20%. from the foregoing table that when substantial quantities of iron and zinc are added t8 an electrolyte containing nickel, the tin precipitated may not be much more than is normally precipitated in a bath containing no nickel,

If a coating of oil or paraflin is placed upon a bath containing substantial quantities of iron and/or mm the tin precipitated in the slim'es is further reduced. Also, if an oxidizing agent, for example hydrogen peroxide, is added to the bath the precipitation of tin in the slimes is accelerated. Thus, it, will be obvious that by I properlycontrolling the several factors involved,

namely, the presence orabsence of nickel or oxidizing agents, the presence or absence of a protective cover on the bath, and the quantity of iron and/or zinc contained in the electrolyte, the ratio between the tin held in'solution in the electrolyte and the tin precipitated in the anode slimes' may be accurately controlled within fairly wide limits.

While benzene disulphonic' acid has been dis closed as 'a sulphonic acid suitable for use in practising the process of the invention, another similar sulphonic acid, for example; phenol sulphonic acid, may be used in substantially the same proportions with satisfactory results The aromatic sulphonic acids are preferably used in erconsumption and their stability makes them economical to use because they may be recovered and reused.

Among the aromatic sulphonic acids which may beemployed' are the mono and poly sulphonic acids of phenol, benzol (benzene), toluol (toluene), the cresols, the xylenes, the xylenols,

naphthalene, the naphthols, anthracene, phenanthrene, and related compounds. The related choro and nitro sulphonic acids of aromatic hydrocarbons may, likewise, be used. In addition, satisfactory results may be obtained by using other acids which dissolve copper, lead and tin, such, for example as pyroligneous. hydrofluosil'icic and fluoboric acids and the sulphonic acids of aliphatic compounds like methane, ethane, propane, etc.. Mixtures of these acids may, of course, be used if desired, and it is within the purview of themvention to employ any acid which forms soluble salts of copper, lead and tin It will be noted I product of the direct sulphonation .of phenol,

containing a mixture of mono and disulphonated phenol with perhaps small amounts of even higher sulphonation products, and in which may be present any one or two or all three of the diacids.

The anode slimes resulting from the practice of the foregoing processes are removed at suitable intervals from the electrolytic cells and are .treated to recover the residual metals contained therein. A suitable process for this purpose, which is described in greater detail in the aforesaid application Serial No. 197,209, will now be described. I The anode slimes are washed, dried, roasted to oxidize the copper content, and leached with benzene disulphonic acid to remove the copper. The leachings and washings are returned to the cells or are used to make up fresh solution.

The leached residues are smelted'to metal in any approved manner and furnace and are cast into anodes, which consist principally'of .tin and may contain a substantial quantity of lead and smaller amounts of antimony, copper and other admixtures. It is preferable that the anodes contain not over about 12% of antimony, copper and other admixtures taken together. Y

For the electrolysis of such materials it is preferable to use phenol sulphonic acid free from sulphuric acid and sulphates. phenol sulphonic acid employed; may be the purified'product of .the direct sulphonation of 'phenol, containing a mixture of mono and disulphonated phenol with perhaps small amounts of even higher sulphonation products, and in which may be present any one or two -or all threeof the di-acids.

A preferred bath for this electrolysis will con-' tain from about 150 to about 350 grams per liter of the phenol sulphonic acid. The bath is improved for the production of good cathodes by the addition of such agents as glue, resorcinol oi" sisting of iron and zinc to be in solution in the bath during the electrolysis in 'sumcient amount In practice, the

the like. In one instance the addition to thebath of from about 0.075 to about 0.10 gram per liter each of glue 'andresorcinol was found to improve materially the .mechanical quality of the cathodes.

.Tnis electrolysis produces substantially pure cathodes of tin or solder according to the composition of the anodes use'd. Substantially all of the antimony, copper and other admixtures, together with some tin and lead, comes out as anode slimes which may be treated in any suitable matter to recover their components.

What is claimed is:

1. The method of separating metals from tincontaining metallic materials consisting principally of copper, which comprises electrolyzing anodes of such a'material in a bath having an aromatic sulphonic acid as principal electrolytic agent to deposit substantially pure' copper, and causing material selected from the group conto effect the holding in solution of a material quantity of tin which would otherwise be precipitated as anode slimes.

2. The method of separating metals from tin- I containing metallic materials consisting prin cipall'y' of copper, which comprises electrolyzing anodes of such a material in a bath having an aromatic sulphonic acid as principal electrolytic agent, and causing iron to be in solution in the bath during the electrolysis in suflicient amount to effect the holding in solution of a material quantity of tin which would .otherwise be precipitated as anqde slimes. 3. The method of separating metals from tincontaining metallic materials consisting principally of copper, which comprises electrolyzing anodes of such a material in a bath having an aromatic sulphonic acidas principal electrolytic agent, and causing zinc to be in solution in the bath during the electrolysis in sufiicientamount to effect the holding in solution of a material quantity of tin which would otherwise be precipitated as anode slimes.

4. The method of separating metals from tin- -containing metallic materials consisting prin-- cipally of copper, which comprises electrolyzing anodes of such a material ina bath having henzene disulphonic acid as" principal electrolytic agent to deposit substantially pure copper and causing material selected from the group consisting 'of iron and zinc to be in solution in the bath during the electrolysis in suflicient amount to effect the holding in solution of a material quantity of tin which would otherwise beprcipitated as anode slimes.

5. The method of separating metals from tincontaining metallic 'materials :consistingprinr cipally 01 copper and containing a quantity of nickel suflicient to materially promote the precipitation of tin as anode slimes, which comprises electrolyzing anodes of such a material in a bath' having an aromatic sulphonic acid as principal electrolytic agent to deposit substantially pure copper, and causing material selected from the group consisting of iron and zinc to be in solution in the bath during the electrolysis in sufiicient amount to effect the holding-in solution of a material quantity of tin which would otherwise" be precipitated as anode slimes.

6. The method of separating metals from tinc'ontaining metallic materials consisting principally of copperand containing a quantity of nickel sufllcient to'materially promote the pre' cipitation of tin as anode slimes, which comprises electrolyzing anodes of such a material in a bath having benzene disulphonic acid as principal electrolytic-agent to deposit substantially pure copper, and causing material selected from. the group consisting of iron and zinc to be in solution in the bath during the electrolysis in suflicient, amount to effect the holding in solution of a material quantity of tinwhich would otherwise be precipitated as anode slimes.

7. The method of separating metals from tin- I containing metallic materials consisting principally of copper, which comprises forming anodes of such a material, .electrolyzing the anodes in a bath having an aromatic sulphonic acid as principal electrolyticagent to deposit substantially pure copper, causing material selected from the group consisting of iron and zinc to be in solution in the bath during the electrolysis. and regulating the concentration of such material throughout the electrolysis a predetermined ratio between tin precipitated as anode slimes and tin dissolved in the bath, the tin dissolved in the bath comprising a material quantity of tin which would otherwise be precipitated as anode slimes.

8. The method of separating metals from tincontaining metallic materials consisting principally of copper, which comprises forming anodes of such a material, electrolyzing the anodes in a bath having benzene disulphonic acid as principal electrolytic agent to deposit substantially pure copper, causing material selected from the group consisting of iron and zinc to be in solution in the bath during the electrolysis, and regulating the concentration of such material in the bath so as to maintain substantially throughout the electrolysis a predetermined ratio betwen tin precipitated as'anode-slimes and tin dissolved in the bath, the tin dissolved in the bath comprising a'material quantity of tin which would otherwise be precipitated as anode slimes.

9. The method of separating metals from tincontaining metallic materials consisting principally of copper, which. comprises forming -anodes of such a material. electrolyzing the in the bath, the tin dissolved in the bath comprising a material quantity of tin which would otherwise be precipitated as anode slimes;

terial in the bath so as to efiect the holding in solution ofthe maximum amount of tin which would otherwise be precipitated as anode slimes.

13 The method of separating metals from tin containing metallic materials consisting principally of coupper, and including a quantity of nickel sufilcient to materially promote the precipitation of tin as anode slimes, which comprises electrolyzing anodes of such a material in a bath having an aromatic sulphonic. acid as principal electrolytic agent to deposit substantially pure copper, and causing material selected from the group consisting of iron and zinc to be in solution in the bath during the electrolysis in sufllcient amount to substantially completely inhibit the tin-precipitating effect of the nickel and thereby efiect the holding in solution of a, material quantity of tin which would otherwise be precipitated as anode slimes.

14. The method of separating metals from tincontaining metallic materials .consisting prinprincipal electrolytic agent to deposit substantially purecopper, and causing material selected from the group consisting of iron and zinc toibe in solution in the bath during the electrolysis in suflicient amount to substantially completely inhibit the tin-precipitating effect of the nickel and thereby effect the holding in solution of a 10; The method of separating metals from tinl containing 'metallic materials consisting principallyof copper, which comprises forming anodes of such a material, electrolyzing the anodes in a bath having an aromatic sulphonic acid as principal electrolytic agent to deposit substantially pure copper, causing zinc to be in solution in the bath duringthe electrolysis, and

regulating the concentration of the zinc in the bath so as to maintain substantially-throughout the electrolysis a predetermined ratio between tin precipitated as anode slimes and tin dissolved in the bath, the tin dissolved in the bath comprising .a material quantity of tin which would otherwise-be precipitated as anode slimes.

11. The method of separating metals from tincontaining metallic materials consisting principally of copper, which comprises forming anodes of such a material, electrolyzing the anodes in a bath having an aromatic sulphonic acid as principal electrolytic agent to deposit substantially pure copper, causing material selected from the group consisting of. iron and zinc to be in solution in the bath during the 'electroylsis,

ill)

andregulating the concentration of such mamaterial quantity of tin which would otherwise be precipitated as anode slimes. i

15. The method of separating metals from metallic materials consisting principally of copper and containing metal of the group consisting of tin'and alloys of tin and lead, which comprises forming anodes of such a material, electrolyzing the anodes in a bath-having benzene disulphonic acid as principal electrolytic agent to deposit substantially pure copper, causing material selected from the group consisting of iron and zinc to be in solution in-the bath during the electrolysis, regulating the concentration of such material in the bath so as to maintain substantially throughout the electrolysis a predetermined ratio between tin precipitated as anode slimes and tin dissolved in thebath, the tin dissolved in the bath comprising a material quantity of .tin which would otherwise be precipitated as anode slimes, forming metallic anodes from the anode slimes, and electrolyzing the last named anodes, in a bath having phenol sulphonic acid as prinliter of metal selected from the group consisting,

of iron and zinc to be in solutionin the bath during the electrolysisto restrain precipitation of tin which would otherwise be precipitated as anode slimes.

17. The method of separating metal from tincontaining metallic materials consisting principally of copper, which comprises electrolyzing anodes of such a mixture in a bath having an aromatic sulphonic acid as principal electrolytic agent to deposit substantially pure copper, causing material selected from the group consisting of iron and zinc to be in solution in the bath during the electrolysis, and regulating the concentration of such material within the range of from about 3 grams per liter to about 28 grams per liter so as to maintain substantially throughout the electrolysis a predetermined ratio between tin precipitated as anodesl'imes and tin dissolved in the bath.

18. The method of separating metal from tincontaining metallic materials consisting principally of copper, which comprises electrolyzing anodes of such a mixture in a bath having benzene disulphonic' acid as principal electrolytic agent to deposit substantially pure copper,- causing material selected from the group consisting of iron and zinc to be in solution in the bath during the electrolysis, and regulating the concentration of such material within the range of from about 3 grams per liter to about 28 grams per liter so as tomaintain substantially throughout the electrolysis a predetermined ratio between tin precipitated as anode slimes and tin dissolved in the bath.

19. The method of separating metal from tincontaining metallic materials consisting principally of copper, which comprises electrolyzing anodes of such a material in a bath having from about 350 to about 500 grams per liter of the acid radical of benzene disulphonic acid as principal electrolytic agent to deposit substantially pure copper, and causing amterial selected from the group consisting of iron and zinc to be in solution in the bath during the electrolysis in suflicient amount to effect the holding in solution of a material quantity of tin which would otherwise be precipitated as anode slimes.

JAMES R. STACK. 

